.223 Remington vs. 5.56x45

Discussion in 'AR15' started by madcratebuilder, Jan 2, 2009.

  1. madcratebuilder

    madcratebuilder G&G Newbie

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    This subject comes up from time to time. I ran across this article on 6mmbr.com. Covers it very well.



    .223 Remington vs. 5.56x45--Chambering and Throat Considerations
    Is the .223 Remington the same as the 5.56x45? The answer is yes and no. There ARE differences between the .223 Remington as shot in civilian rifles and the 5.56x45 in military use. While the external cartridge dimensions are essentially the same, the .223 Remington is built to SAAMI specs, rated to 50,000 CUP max pressure, and normally has a shorter throat. The 5.56x45 is built to NATO specs, rated to 60,000 CUP max pressure, and has a longer throat, optimized to shoot long bullets. That said, there are various .223 Remington match chambers, including the Wylde chamber, that feature longer throats. Military 5.56x45 brass often, but not always, has thicker internal construction, and slightly less capacity than commercial .223 Rem brass.
    Should you be worried about shooting 5.56x45 milspec ammo in a .223 Remington? The answer really depends on your chamber. 5.56 x45 ammo is intended for chambers with longer throats. If you shoot hot 5.56x45 ammo in short-throated SAAMI-spec chambers you can encounter pressure issues. The new long-throated 'Wylde' chamber allows safe use of military ammo. Wylde chambers are quite common in Rock River guns. Other manufacturers, such as Fulton Armory, offer modified "match chambers" with extended throats that allow safe use of 5.56x45 ammo in .223 Remington rifles. For a complete discussion of the .223 Rem vs. 5.56x45 question, read this Tech Notice from Winchester, and this GunZone Commentary by Dean Speir. Without belaboring the point, we'll repeat the official SAAMI position: "Chambers for military rifles have a different throat configuration than chambers for sporting firearms which, together with the full metal jacket of the military projectile, may account for the higher pressures which result when military ammunition is fired in a sporting chamber. SAAMI recommends that a firearm be fired only with the cartridge for which it is specifically chambered by the manufacturer."
  2. jv101

    jv101 G&G Newbie

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    Good post!
  3. 338RUM

    338RUM G&G Enthusiast

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    thanks very informative!!!!
  4. texnmidwest

    texnmidwest Sir Loin of Beef Forum Contributor

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    Great Post! Thanks.
  5. SwedeSteve

    SwedeSteve Freedom Zealot Forum Contributor

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    Thanks for the info !! Hopefully someone will make it a sticky !!
  6. Soldier Medic

    Soldier Medic G&G Newbie

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    Thanks for clearing that up, I really hope people just fire the ammunition the manufacturer intended their AR15's fire. The only way I would switch over ammunition is if it were an emergency situation, i wount switch if I am low on my .223 Rem. Its gottah be a Zombie vs Me and im out of ammo! Lol.
  7. tommy

    tommy G&G Newbie

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    so this is just me thinking here but to me the 5.56 round is good for your long range shooting and body shots but if you want really tight groups the .223 is a better more accurate round. or can you get the same accuracy from both rounds???
  8. G23c

    G23c G&G Newbie

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    Good information, thanks.
  9. Robert Seccombe

    Robert Seccombe G&G Newbie

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    Before the 223 Remington

    The cartridge on the left is the Winchester .224E2 and the cartridge on the right is the 222 Remington Special (which became the 223 Rem)

    Attached Files:

  10. tommy

    tommy G&G Newbie

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    has anyone givin my thought any thought about the .223 being a more acurate round than the 5.56. i was thinkin of getting a few boxs of .223 and trying them out to see how they group and then trying out some 5.56 round with the same weight.
  11. 147 Inches

    147 Inches G&G Newbie

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    Accuracy depends on many things.
    Rate of twist, lenght of barrel, grain of bullet among other things.
    I personally think you are splitting hairs between a .223 and a 5.56.

    Marines can hit a target with a 5.56 that I couldn't even see and with iron sights.
    That accuracy is plenty good enough for me.

    Here's what I got.

    Bushmaster, 20" 1/9 twist H Bar

    I just joined a range that I can fire up too 200 yards on a regular basis, 300 yards at special shoots.
    Before that I was limited to 38 yards and 80 something yards.
    I never saw a difference in accuracy, but I will remember your post and give it another try in the spring.
    This is what I have fired:

    Federal XM193 FMJ 55gr.
    PMC .223 62gr.?? (I think)
    Remington UMC .223 50 gr.
    American Eagle XM193 FMJ 55gr.
    ADCOM 5.56 M855 62gr.
  12. f8talh8red

    f8talh8red Suspended

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    all rifles that are clearly marked .223 should only shoot .223. if your rifle is in 5.56 you can shoot both and will be ok. my oly k3b is marked multi wich means i can shoot either or. ill bet the .223 is a little more accurate, but im not an expert.
  13. Aznative

    Aznative G&G Newbie

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    One interesting item concerning the pressure differences between 5.56 and 223 is the difference in the way the military measures pressure vs sammi. The military measures pressure at the bolt face and Sammi measures it at the front of the chamber. So comparing 60,000 psi for military cartridges vs 50,000 for 223 cartridges, is like comparing apples to oranges.
  14. wunhunglo

    wunhunglo G&G Newbie

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    One of the critical things deciding accuracy in 'factory ammunition' both commercial & milspec is how close the tolerances they manufacture it to are. I've used mil-surp which has been better than lots of commercial ammo. Just a case of find what suits you best & how much you want to spend. One of the slight advantages of using nato marked ammo is that you at least know that it is manufactured to a recognised standard.
    So yes, you can get the same accuracy from both mil spec 5.56 & .223 commercial ammo.
  15. Big Dog

    Big Dog Dinosaur Wrangler Forum Contributor

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    My Bushpup shows better accuracy, on the average, using good US-made commercial .223Rem than with most Surplus 5.56. I put this up to better QC and more consistency.
    My handloads using both cases, with same bullet and powder load, show the same accuracy. I do NOT load to max pressure - mid level between MIN and MAX loads generally works best for me.
  16. wunhunglo

    wunhunglo G&G Newbie

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    I think that some mention should be made of the different 5.56 ammo. Seems to be come confusion with some people referring to 5.56 as 5.56 Nato.

    Most common American produced 5.56 ammo is XM193 and is loaded with a 55gn bullet which is loaded to around maximum .223 pressures; many people find no problems using this ammo in a .223 chamber.

    5.56 Nato is different and the normal ball ammo is loaded with a 62 gn bullet, commonly known as M855 or SS109, this is Nato spec ammo, marked with the Nato symbol (+ in a circle) and loaded to higher pressures.
    This ammunition should never be used in a .223 chambered rifle.
  17. drifter

    drifter G&G Newbie

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    I realize I'm getting to this party way late, but maybe this will help someone else not have the same problems. Or maybe I'm even later than I think and it's already been covered here.
    I got 500 rounds of Wolf coated steel case marked only as 'Wolf .223' and had to wait to get on an outside range where I could try it after I discovered it was steel. More than one round every 10 seconds or so and it'll stick the empty in the chamber. I was warned but got carried away. Ooops. The empty will pop right out with a cleaning rod after it's cooled off. Filthy ammunition though. Half a grocery bag of used patches to get the crud out of the barrel and I'm concerned about the gas tube, but not sure what to do about cleaning the little bugger.
    Another no-no for my rifle is Winchester White box from Wally World. Many of the cases in the batch I had measured several thousandths wider that they're supposed to be, checking unfired rounds after the fact, and that was my first adventure sticking an empty.
    The rifle is a S&W M&P 5.56, and a gem to shoot with good ammo.
  18. ZombieHunter

    ZombieHunter Suspended

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    I hate to break it to you, but you should NEVER use 5.56 ammo in anything that isn't labeled to fire 5.56 ammo. You just don't do it. The case is thicker, which results in higher pressure buildup.

    The difference between M193 and M855 is simply the slug used in the cartridge. Most modern firearms will have no problem firing a 5.56 round from a .223, just as most police-issue kevlar vests will have no problem stopping a 9mm round...but just the same, you shouldn't go testing this theory by having people shoot you in the chest. Likewise, you don't test it by firing ammo not designed for your chamber, unless specified suitable by the manufacturer of the firearm (as done by Ruger with their Mini-14).

    The only serious difference between "NATO-spec 5.56" and M193 is the fact that M855 fires a heavier steel-core slug designed for penetration of steel...
  19. tenringdriller

    tenringdriller G&G Newbie

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    specifically they were designed to penetrate a steel helmet at 600 meters, don't go thinking you can saw open a tank with the m855. Also, the addition of a steel core made the projectile less likely to yaw and fragment, decreasing the wounding and zombie-killing potential. better off with the ss109, which has a tendency to fragment at the cannelure (the crimping groove)....that is if you own a military rifle for what it's meant to do: kill bad guys. (or the undead)
  20. wunhunglo

    wunhunglo G&G Newbie

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    Last edited: Oct 24, 2009
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